1. Field of the Invention
The present invention relates to a low voltage circuit breaker which is so-called molded case circuit breaker, and particularly, to a case for a circuit breaker with a monolithic door capable of simply changing a terminal structure according to a wire engaging method.
2. Background of the Invention
In general, a circuit breaker applied to a power system may be provided with a terminal portion for engaging a power source side wire and a electric load side wire. The circuit breaker may have, according to a wire engaging method, an upper engaging-type terminal portion (so-called standard type terminal portion), a rear engaging-type terminal portion, a plug-in type terminal portion and a lug type terminal portion.
A circuit breaker with a structure capable of replacing various terminal portions according to the wire engaging method and a case therefor according to the related art will be described with reference to the accompanying drawings.
First, the related art will be described with reference to FIGS. 1 and 2.
FIG. 1 is a perspective view illustrating a circuit breaker according to the related art and a case therefor, particularly, a partially-cut perspective view illustrating a terminal portion, and FIG. 2 is a view illustrating a circuit breaker according to the related art and a case therefor, particularly, an operational state view illustrating that a terminal block is assembled to or separated from a terminal portion.
Regarding a circuit breaker 1 according to the related art illustrated in FIG. 1, a case therefor may include a lower case 2 and an upper cover 3. A reference numeral 6 designates a terminal block provided at each of front and rear surfaces of the circuit breaker 1 for engaging external wires of power source side and electric load side.
Explaining an operation of mounting (assembling) the terminal block portion 6 to the circuit breaker 1 according to the related art with reference to FIG. 2, an upper engaging-type terminal portion (so-called a standard type terminal portion) is exemplarily shown in FIG. 2. The terminal block portion 6 is inserted into the circuit breaker 1 in a rear direction indicated by an arrow based upon the drawing in a state of having a nut 7 being mounted thereon.
In more detail, rail engaging portions (reference numeral not given) formed by both lateral concave portions between upper and lower plates of the terminal block portion 6 are slid onto mounting rails (reference numeral is not designated) which are installed at the lower case 2 below a terminal portion T of a fixed contactor which is exposed to front and rear surfaces of the circuit breaker 1 and provided on each of three phases, such that the rail engaging portions can be supported by the mounting rails. Accordingly, the terminal block portion 6 is assembled to the circuit breaker 1 of the related art.
Here, terminal block protrusions 6a formed on the lower plate of the terminal block portion 6 intensify a contact force between the rail engaging portions of the terminal block portion 6 and the mounting rails at the lower case 2.
An unexplained reference numeral 3 in FIG. 2 designates the upper cover previously described in FIG. 1.
Both in the related art and in the present invention, various types of terminal blocks can be mounted in the circuit breaker, which will be described with reference to FIGS. 3 to 6.
A terminal block shown in FIG. 3 designates a standard type terminal block portion 6-1 which is a terminal block having an upper face (surface) to which an external wire of either a power source or an electric load is engaged. It is characteristic that a nut (refer to the numeral 7 in FIG. 2) is mounted on its upper face.
A terminal block shown in FIG. 4 designates a rear engaging-type terminal block portion 6-2, which is a terminal block in a shape that an external wire of the power source or the electric load is engaged to short rear engaging-type terminal and long rear engaging-type terminal (refer to 6-2a and 6-2b in FIGS. 8 and 9) each of which is extended downwardly from a terminal block (not shown). Unlike the standard type terminal block portion 6-1, this rear engaging-type terminal block portion 6-2 does not have the nut but has an insertion hole in which an upper hexagonal end portion of the short or long rear engaging-type terminal is inserted.
A terminal block shown in FIG. 5 designates a plug-in type terminal block portion 6-3, which is a terminal block in a shape that an external wire of power source or the electric load is engaged to a plug-in type terminal (not shown and refer to 6-3a in FIG. 11) extended downwardly from the terminal block. Unlike the standard type terminal block portion 6-1, this plug-in type terminal block portion 6-3 does not have the nut but has an insertion hole in which an upper hexagonal end portion of a plug-in type terminal is inserted.
A terminal block shown in FIG. 6 designates a lug type terminal block portion 6-4 in a shape that an external wire of the power source or electric load is connected in a lug (refer to the numeral 6-4a in FIG. 13). It is characteristic that the upper surface of the terminal block portion 6-4 is wide and flat suitable for the installation of a terminal portion of a fixed contactor (refer to T in FIG. 2).
FIG. 7 is a view illustrating a circuit breaker according to the related art and a case therefor, particularly, a state view illustrating an operation that an external wire is connected to a terminal portion having a standard type terminal block mounted, explanation of which will be given as follows.
The operation of mounting the standard type terminal block can be understood by the description made with reference to FIG. 2.
After mounting the standard type terminal block, the following operation is performed such that external wires of the power source or electric load (in detail, six wires in all including three power source side three-phase wires and three electric load side three-phase wires) are engaged to terminal portions exposed to front and rear surfaces of the lower case 2 of the circuit breaker.
That is, as shown in the drawing, a wire terminal W1 of an external wire W is placed on an exposed terminal portion (reference numeral not given) of a fixed contactor.
A coupling screw S is inserted into (passed through) the wire terminal W1 to be coupled (engaged) to a screw engaging hole (not shown) formed in the terminal portion of the fixed contactor.
Accordingly, the external wire W can be electrically connected to the fixed contactor terminal portion so as to complete the wire connection.
With reference to FIGS. 8 to 10, explanation will be made of a rear connecting-type terminal block according to the related art and the construction of a case for a circuit breaker having the rear connecting-type terminal block, and an operation of mounting the rear connecting-type terminal block according to the related art to the case for the circuit breaker.
Description will be given of an operation of first removing a standard type terminal block having mounted and mounting a rear engaging-type terminal block with reference to FIG. 10 as follows.
FIG. 10 is a view illustrating a circuit breaker according to the related art and a case therefor, particularly, a perspective view shown from a lower side of the circuit breaker with an inclination angle which illustrates an operation of removing is a standard type terminal block and mounting a rear connecting-type terminal block and a rear connecting-type terminal.
First, as illustrated in FIG. 10, a standard type terminal block portion 6-1 is removed in a direction indicated by an arrow.
The rear engaging-type terminal block portion 6-2 is mounted where the removed standard type terminal block portion 6-1 has been disposed.
An upper end hexagonal engaging portion either of a short rear connecting-type terminal 6-2a or a long rear connecting-type terminal 6-2b is upwardly inserted from a lower side of the rear connecting-type terminal block portion 6-2.
The upper end hexagonal connecting portion of the rear connecting-type terminal 6-2a or 6-2b is rotated for insertion such that the upper end hexagonal connecting portion can be accurately connected with an inner hexagonal connecting hole of the rear connecting-type terminal block portion 6-2. Accordingly, the rear connecting-type terminal block portion 6-2 is connected to the rear connecting-type terminal 6-2a or 6-2b. 
A coupling screw S is inserted into a screw engaging hole (not shown) of the terminal portion of the fixed contactor and a female screw hole (not shown) formed in an upper end portion (head portion) of the rear connecting-type terminal 6-2a or 6-2b so as to be coupled thereto.
Accordingly, the connecting between the rear connecting-type terminal 6-2a or 6-2b and the rear connecting-type terminal block portion 6-2 can firmly be maintained.
For additional reference, external wires may be connected to the rear connecting-type terminal 6-2a or 6-2b by a method for inserting the wires through a wire connecting hole formed in a lower end portion of the rear connecting-type terminal 6-2a or 6-2b. 
In another connecting method, a busbar-type wire is placed on the lower end portion of the rear connecting-type terminal 6-2a or 6-2b. A bolt is inserted through both the wire connecting hole and the busbar-type wire to be fixed by a nut, thereby engaging the wire to the terminal.
With reference to FIGS. 11 and 12, the following description will be given of constructions of a plug-in type terminal block and a case for a circuit breaker having the same according to the related art, and an operation of mounting the plug-in type terminal block at the case for the circuit breaker according to the related art.
An operation of first removing a standard type terminal block having mounted and mounting a plug-in type terminal block will be described with reference to FIG. 11.
FIG. 11 is a view illustrating a circuit breaker and a case therefor according to the related art, particularly, a perspective view shown from a lower side with an inclination angle which illustrates an operation of removing a standard type terminal block and mounting a plug-in type terminal block and a plug-in type terminal.
First, as illustrated in FIG. 11, the standard type terminal block portion 6-1 is removed in a direction indicated by an arrow.
The plug-in type terminal block portion 6-3 is mounted where the removed standard type terminal block portion 6-1 has been disposed.
An upper end hexagonal connecting portion of the plug-in type terminal 6-3a is upwardly inserted from a lower side of the plug-in type terminal block portion 6-3. Accordingly the plug-in type terminal 6-3a is connected to the plug-in type terminal block portion 6-3.
A coupling screw S is inserted into a screw engaging hole (not shown) of the terminal portion of the fixed contactor and a female screw hole (not shown) formed in an upper end portion (head portion) of the plug-in type terminal 6-3a so as to be coupled thereto.
Accordingly, the connecting between the plug-in type terminal 6-3a and the plug-in type terminal block portion 6-3 can firmly be maintained.
Description will be given with reference to FIG. 12 of an operation of engaging a circuit breaker having a plug-in type terminal block and a plug-in type terminal according to the related art and its case to a plug-in connecting base as follows.
Referring to FIG. 12, a plug-in connecting base B may include plug-in insertion holes B2 for engaging plug-in terminals of the circuit breaker having a plug-in type terminal, and a plurality of engaging terminals B1 disposed at front and rear surfaces for connecting external wires of either a power source side or a electric load side.
The plug-in connecting base B as illustrated in FIG. 12 may be a base to which not only the case for the circuit breaker having the plug-in type terminal according to the related art but also a case for a circuit breaker having a plug-in type terminal according to the present invention can be engaged.
An operation of connecting the plug-in terminal of the circuit breaker having a plug-in type terminal to the plug-in connecting base B can be done by pressing and inserting the plug-in terminal of the circuit breaker into the plug-in insertion hole B2 from an upper side of the plug-in connecting base B.
An operation of connecting a lug-type terminal block and a lug according to the related art will be explained with reference to FIG. 13 as follows.
Explaining that a lug-type terminal block portion 6-4 is assembled to a circuit breaker 1 according to the related art with reference to FIG. 13, first, the lug-type terminal block portion 6-4 is inserted into the circuit breaker 1 in a direction to a rear surface side based upon the drawing.
In more detail, rail engaging portions (reference numeral not given) formed by both concave portions between upper and lower plates of the lug-type terminal block portion 6-4 are installed onto mounting rails (reference numeral not given) which are installed at the lower case 2 below a terminal portion T of a fixed contactor, each of which is exposed to front and rear surfaces of the circuit breaker 1 and provided on each of three phases, such that the rail engaging portions can be supported by the mounting rails. Accordingly, the lug-type terminal block portion 6-4 is assembled to the circuit breaker 1 of the related art.
The lug 6-4a is inserted in a direction to a rear surface side based upon the drawing such that it can be positioned on the terminal portion T of the fixed contactor.
Regarding the case for the terminal structure changeable circuit breaker the according to the related art which is configured and mounted as mentioned above, from the perspective of manufacturers of the circuit breakers or installation operators of the circuit breakers, the terminal blocks should be provided according to their types to be suitable for each wiring method. Accordingly, they should keep sufficient amount of the terminal blocks according to their types in order to supply them when required.
In addition, in the case for the terminal structure changeable circuit breaker the according to the related art, each type of terminal block has a similar structure, which make it difficult for those who have not instructed or have no experience of classification to accurately classify and use the terminal blocks.
In the case for the terminal structure changeable circuit breaker the according to the related art, each type of terminal block has a very small size with a horizontal or vertical length of 1 to 3 centimeters. Also, these tiny components are fabricated separately from the case for the circuit breaker to be thereafter assembled thereto. Accordingly, it is easy to lose the terminal blocks.
Therefore, the manufacturers or installation operators of the circuit breakers need to make personal, temporal or physical efforts for preventing the loss.
Furthermore, a separation preventing structure between a terminal block and a case, for example, a separation preventing protrusion with strong intensity for preventing the separation of the terminal block while being used is generally configured. Accordingly, if the terminal block is required to be replaced while being used, when separating the terminal block to be replaced by an excessive force or by using a certain device, the terminal block or the case for the circuit breaker may be damaged.
In addition, if the separation preventing structure between the terminal block and the case is changed into a structure that can easily be separated by weak outer force, due to the difficulty of the replacement, the terminal block may easily frequently be separated from the case.